We shall continue our efforts to study the genetic organization of mammals, including man, using somatic cell genetic techniques. Efforts will be made to develop further our capacity to map genes directly using complementary sequence probes. We shall particularly focus on human histone genes and mouse nucleolar organization genes during the next twelve month period. Efforts will continue in our attempts to physically isolate the transgenome from unstable, transformed cell lines. We believe this might be accomplished within the next year. Such a technical achievement will allow the characterization of the transgenome in terms of its replicon structure, size, ang general form. This information is basic to our understanding of its transmission and integration into the host genome. BIBLIOGRAPHIC REFERENCES: Shimizu, Nobuyoshi, Richard E. Giles, Raju S. Kucherlapati, Yoshiko Shimizu, and Frank Ruddle. Somatic Cell Genetic Assignment of the Human Gene for Mitochondrial NADP-linked Isocitrate Dehydrogenase to the Long Arm of Chromosome 15. Somatic Cell Genet. 3: 47-60, 1977. Kozak, C.A. and F.H. Ruddle. Assignment of the genes for thymidine kinase and galactokinase to Mus musculus chromosome 11 and the preferential segregation of this chromosome in Chinese hamster/mouse somatic cell hybrids. Somatic Cell Genet. 3: 121-133, 1977.